I went into my Symantec Endpoint Protection Manager to change the firewall policy , opening ports 135 and 445 so that WMI can work.

I left it to trigger overnight and today , I appear to be able to get the software on my PCs . There were some with authentication problems and I settled that with additional scan credentials . Seems like everything is coming in now . Will know better after I final check every PC. Currently occupied with other projects , so will come back to this in a few days.

In the meantime , I thank all who have helped to point the way . Thanks